Pull out typewriter supports



June 14, 1955 I M. E. CHAFT 2,710,732

PULL OUT TYPEWRITER SUPPORTS 3 Sheets-Sheet 1 Filed Aug. 25, 1951INVENTOR. MARC E CHA FT ATTORNEY M. E. CHAFT "2,710,782 r I :5Sheets-Sheet 2 IN V EN TOR.

ATTORNEY PULL ou'r TYPEWRITER SUPPORTS June 14, 1955 Filed'Aug; as 1951United States atent Patented dune 14, 1955 liee This invention relatesto pull out typewriter supports. It is particularly directed to a deskhaving means to support a typewriter within the desk, at a relativelylower level, and means to permit the typewriter support to be pulled outin front of the desk and raised to a higher level and maintained at suchlevel, so that the typist may use the typewriter.

An object of this invention is to provide a highly improved device ofthe character described, including common spring means for both raisingand lowering the typewriter support, and for yieldably retaining thesupport in raised or lowered position.

A further object of this invention is to provide in a device of thecharacter described, highly improved locking means for preventingraising of the typewriter support until it is pulled forwardly to apredetermined position, said means being releasable when the typewritersupport or table is pulled forward to such position, thereby permittingraising of the typewriter support or table to its higher level in frontof the desk.

Still another object of the present invention is to provide in a deviceof the character described, a pair of aligned horizontal rails, acarriage supported on the rails by means of rollers for forward andbackward movement, a horizontal typewriter table fixed at its rear endto the carriage and extending forwardly thereof, means to permitswinging of the rails from a lower to a higher position, means to locksaid rails in its lower position, said means being releasable by movingthe carriage and table forwardly to a predetermined position to releasethe locking means to permit swinging of the rails upwardly, and means onthe carriage to retain the typewriter table in its forwardly pulledposition, and to prevent side sway of the typewriter table while it isbeing swung upwardly.

Yet another object of this invention is to provide in a device of thecharacter described releasable catch means to lock the typewriter tablein its raised position and to prevent side sway of the typewrite tablewhile it is being used in its raised position.

Still a further object of this invention is to provide a device of thecharacter described which shall be relatively inexpensive tomanufacture, easy to manipulate, smooth and positive in operation, andyet practical and eflicient to a high degree in use.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

The invention accordingly consists in the features of construction,combinations of elements, and arrangement of parts, which will beexemplified in the construction hereinafter described, and of which thescope of invention will be indicated in the following claims.

In the accompanying drawings in which are shown various illustrativeembodiments of this invention,

Fig. l is a vertical cross-sectional view of a desk provided with a pullout typewriter support embodying the invention, and showing the supportin lowered position;

Fig. 2 is a partial view of Fig. l with the support pulled forwardly butnot fully;

Fig. 3 is a view similar to Fig. l, but showing the support in raisedposition;

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 1;

Fig. 5 is a cross-sectional view taken on line 5-5 of Fig. 1;

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 1;

Fig. 7 is a cross-sectional view taken on line 7-7 of Fig. 1;

Fig. 8 is a cross-sectional view taken on line 88 of Fig. 1;

9 is a cross-sectional view taken on line 9-9 of Fig. 1;

Fig. 10 is a of Fig. 1;

Fig. 11 is an enlarged sectional View illustrating the table catch;

cross-sectional view taken on line 1il10 Fig. 12 is a cross-sectionalview taken on line 1212 of Fig. 11;

Fig. 13 is a front elevational view of the catch guide; and

Fig. 14 is an elevational view of the catch retainer.

Referring now in detail to the drawing, 10 designates a device embodyingthe invention. The same comprises a typewriter desk 11 which may beprovided with front corner posts 12 and rear corner posts 13. The frontcorner posts 123 have legs 12a at their lower ends and the rear cornerposts 13 have legs 13a at their lower ends. At the upper ends of thelegs 12a, 13a is a bottom, horizontal wall 14. The corner posts 12. and13 are interconnected by side walls 15. The rear corner posts 13 areinterconnected by a rear wall 16. The upper ends of the front cornerposts 12 are interconnected by a horizontal cross bar 18.

Supported by the desk 11 is the pull out typewriter table mechanism 20.The mechanism comprises a pair of parallel, horizontally aligned,similar, symmetrically disposed bars 21 attached at their front ends tothe front corner posts 12 as by screws 22, and attached at their rearends as by screws 23 to the rear corner posts 13. The bars 21 arelocated substantially midway between the bottom wall 14 and the upperend of the desk. The desk may be provided with any suitable top wall(not shown). It will be understood furthermore that the mechanism 2! maybe incorporated into any suitable desk or support, and the onlyattachment of the mechanism 20 to the desk or support is by means of theparallel bars 21.

The bars 21 are formed with outwardly pressed portions 23a locatedcloser to their rear ends than to their front ends. The portions 23a areparallel to the main portions of the bars and are connected to said mainportions by offset shoulder portions 24. Pivoted to the bars 21 as onpivot pins 25, located forwardly of portions 23a, are front bell cranks26. The bell cranks 26 are similar and symmetrically disposed to oneanother. They are located on the inside of the bars 21.

Each bell crank 26 has a portion 27 formed with a through opening 23through which a pivot pin passes. Each pivot pin 25 has a central spacerportion 29 to space portion 27 of the bell crank 26 from the bar 21. Ithas a reduced outer end 30 received in the opening 28 in said portion27, and an opposite reduced end 31 passing through an opening in the bar21. Said reduced ends 30 and 31 are riveted over to keep bell crank 26assembled with the bar 21.

It will now be observed that the portion 27 is in a plane disposedinside of the plane of bar 21. Extending from portion 27 is an arm 32 inthe plane of said portion 2'7. Said arm 32 is formed with a pivotopening 33 for the purpose hereinafter appearing. It will be noted thatthe arms 32 of the bell cranks 26 project forwardly when the typewritertable is in its lower position, as will be ex plained hereinafter.

The portions 27, 32 of each bell crank are in a vertical plane.Extending outwardly from each portion 27 is an offset portion 34 fromwhich extends downwardly and forwardly an inclined portion 35, likewisedisposed in a vertical plane just inside of the plane of the bar 21.Offset inwardly from the lower end of the portion 35 is a portion 36from which extends downwardly a portion 37, likewise disposed in avertical plane. Portion 3'7 is disposed substantially in the plane ofthe portion 27. Fixed to the inner surface of each portion 37 is alocking cam 40 disposed in a vertical plane. The portion 37 and thelocking cam 49 are formed with registering through openings 41 throughwhich extends portion 42 of a pivot pin 43. Portion 37 may be providedwith an extruded pin portion 44 extending through openings in the cam 40for locating said cam.

The cam 40 has a circular outer peripheral edge 45. The peripheral edge45 extends through an angle of about 180 beginning at its forward endfrom a point 46 (Fig. 1) above the level of the pivot pin 43 andextending downwardly and rearwardly around to a point 47 below and inback of the pivot pin 43. Extending from the point 47 upwardly is aninwardly curved peripheral edge 48. The peripheral edge 45 has a radiusabout the axis of pivot pin 43. The cam 40 is preferably hardened andhence is made separately from the bell crank 26 and is fixed thereto asby welding. The extruded pins 44 serve as locating pins for locating thelocking cam 4% relative to the bell crank.

Each pivot pin 43 is formed with a spacer portion 59 at the inner sideof the locking cam 49 and extending therefrom is a reduced portion 50apassing through an opening in a horizontal rail 51. It will now beunderstood that the front portions of the rails 51 are suspended fromthe bars 21 by means of the bell cranks 26. It will now be furtherunderstood that the rails 51 are spaced inwardly of the locking earns 40by means of the spacers 50.

Said rails 51 are also suspended from the bars 21 by means of rear bellcranks 55. It will be noted that there are two rear bell cranks 55 andthat they are similar and symmetrically disposed with respect to oneanother. Each bell crank 55 comprises a portion 56 disposed in avertical plane and inclined forwardly and downwardly at substantiallythe same angle as portions 35 of bell cranks 26. At the lower end ofportion 56 is an outwardly offset portion 57 from which extendsdownwardly a portion 53 disposed in the plane of portion 56. Portion 58is formed with through opening 59 to receive one riveted end 66) of apivot pin 61. The pivot pin 61 comprises an intermediate spacer portion62 and an opposite riveted end 63 passing through an opening in the rail51.

Portion 56 of each bell crank 55 is formed with a through opening 63anear its upper end through which extends a horizontal round bar 64. Bar64 is formed with a spacer collar portion 65 contacting the outersurface of said portion 56. Extending beyond the collar 65, bar 64 has aportion 66. Pivoted on said portion 66 is the lower end of a brace bar68 formed with an opening through which said portion 66 passes. Saidportion 66 also passes through an opening 69 in the fixed bar 21. Theouter end of portion 66 is riveted over as at 79.

Extending upwardly and forwardly from said portion 56 (Fig. l) is aportion 71 formed with a through opening 72. Extending from the opening'72 is a pivot pin 73. Extending through the opening 33 in the forwardlyand upwardly inclined arm 32 of the bell crank 26 is a pivot pin 75.

The forward ends of said portions 32 and 71 of the bell cranks 26 and 55are interconnected by horizontal links 76 formed with openings throughwhich said pivot pins 73 and 75 pass. Each link 76 has an outwardly re-4 cessed portion 77 shorter in length than the outwardly recessedportions 23a of the fixed bars 21 and located between the ends of thelatter. Recessed portions 230 allow clearance for recessed portions 77and the latter allow clearance for pivots 61.

The upper ends of the brace bar 68 are interconnected by a horizontaltransverse rod 89 at their upper ends. Brace links 81 are connected attheir upper ends as by pins 82 to intermediate portions of the braces68. The lower ends of the braces 81 are connected to the rear ends ofthe fixed bars 21 as by said screws 23. Braces 68 are inclinedrearwardly and upwardly from their lower ends. The braces 81 areinclined forwardly and upwardly from their lower ends. Said braces 68and 81 are fixed with relation to the fixed bars 21.

Fixed to the cross bar 64 are a pair of similar symmetrically disposedspring anchor members 88. Each comprises a short arm 89 contacting theinner surface of wall 56 of bell crank 55. The short arm 89 is formedwith a through opening through which the bar 64 passes. Extending fromthe short arm 89 is a portion 90 parallel to bar 64 and disposedthereabove when the parts are in the position shown in Fig. l. Extendingdownwardly from portion 90 is a long arm 92 parallel to the arm 89. Whenthe parts are in the position shown in Fig. 1, arm 92 is inclineddownwardly and forwardly. At the lower end of each arm 92 is a throughopening 93 carrying a pivot pin 94. Pivoted to each pivot pin 94 is ahooked member 95. A line connecting the axis of pivot pin 94 with theaxis of the transverse rod Si is located somewhat rearwardly of the axisof the transverse rod 64 when the parts are in the position shown inFig. l, for the purpose hereinafter appearing. The hooked members 95, inthe position shown in Fig. 1 each has an arm 96 extending upwardly fromthe pivot pin 94 to a position above the rod 64.

Extending downwardly and rearwardly from the upper end of arm 96 is anarm 97 formed with an opening 98. Each hooked arm contacts the innersurface of the long arm 92 of one of the brackets 83. The opening 98 isinterconnected to rod 89 by a coil compression spring 100. The shortarms 89 of the brackets 88 are welded to portions 56 of the bell cranks55 so as to be integral therewith and to rotate about the axis of therod 64 together with said rear bell cranks 55.

It will be noted that in the position of Fig. l, the axis of openings 98will be in a line connecting the axis of rivets 94 with the axis of therod 80. The pull of the coil spring 3'09 will therefore tend to swingthe rear bell cranks 55 in a counterclockwise direction, looking at Fig.1, so as to hold the rail members 51 in their rearwardly position andagainst forward movement.

it will be noted that the distance between the axes of pivots 25 and rod64 is the same as the distance between the axes of pivots 43 and 61, andis also equivalent to the distance between the axes of pivots 73 and 75.For this reason the bell cranks 26 and 55 can rotate about their pivots25 and 64 respectively from the position shown in Fig. l, in clockwisedirection, to bring the rails SE from their lowermost position shown inFig. 1 to their uppermost position shown in Fig. 3.

Means is provided, however, to prevent such movcment. To this end therails 51 are each formed at points spaced rearwardly from the pivots 43,with an opening 181 through which extends one end of a pivot pin 102.The pivot pin is formed with a spacer portion 103 contacting the outerside of the rail 51, and is formed with an outwardly extending stem 184.Pivoted to the stem 164 is a locking lever 1S5. Said locking lever 105has a straight lower edge 196. It is formed in its upper side with arearwardly and upwardly inclined slot 107 which is open at its outerend. It is also formed with an outwardly curved peripheral edge 108which is adapted to contact the inwardly curved edge 43 of the bellcrank 26. At the lower end of outwardly curved edge 108 is an outwardlyextending finger 169 which serves as a stop to contact point d7 ofmember 40. Extending from the upper end of the curved edge 1% is aninwardly curved peripheral edge 110 to provide clearance when operatingthe device. The center of curvature of peripheral edge 108 is the axisof pivot 1&2. Therefore, the center of curvature of the peripheral edge48 is likewise the axis of pivot pin 102.

It will now be observed that when the parts are in the position shown inFig. 1, the rails 51 cannot be swung forwardly because edges 16%? of thelocking levers contact edges 18 of the bell cranks 26. It will be noted,furthermore, that the upper lip 112 formed above the slot 107 projectsabove the level of the upper edge of the rail 51, whereas, the finger113 below the slot 107 is normally disposed below the upper edge of therail 51, as shown in Fig. 1 of the drawing.

Fixed to the rails 51 adjacent the lock ng levers 1% are pins 114connected by coil tension springs 115 to openings 116 in the pivotedlocking levers 1 595. The openings 116 are located above the slots 1W.The springs 115 thus tend to rotate the locking levers 165 in clockwisedirections looking at Fig. l. The engagement of fingers N9 with points47 of members 4-0 serve to limit rotation of the locking levers 165 insaid counterclockwise direction.

Mounted on the rails 51 are a pair of carriages 124). The carriages 120are similar and symmetrically disposed so that only one of saidcarriages will be described. Each carriage 120 comprises a vertical wall121 disposed on the inside of the rail 51. The lower edge 12?. of wall121 is disposed below the rail when said rail is in the position shownin Fig. 1. Wall 131 has a rearwardly extending finger 123. Fixed to saidfinger is a horizontal pivot pin 12 i disposed below the rail 51 andextending from the inside thereof, to the outer side thereof. Rotatablymounted on the pivot pin 124; by means of ball bearings is a groovedroller or wheel 125 engaging the underedge of rail 51. Extending fromthe wall 121 is a horizontal wall 126 projecting inwardly of said wall121.

Said wall 121 is formed with an upwardly extending finger 127 from whichextends a horizontal wall 123 located rearwardly of and above the levelof said Wall or flange 12$. interconnecting said carriages 120 andmounted thereon is a typewriter table or support 130. Said table is in ahorizontal position. It rests on top of the flanges 126 and beneath theflanges 123 and is fixed thereto by suitable screws, or in any othersuitable manner. The screws may pass through suitable openings in theflanges 126, 123. low the flange 126 at the forward end of the carriageis a pivot pin 132 passing above the rail 51 from the inside to theoutside thereof. Rotatably mounted on pivot pin 132 is a grooved rolleror wheel 133 contacting the upper edge of the rail 51.

' It will now be understood that the carriages 1253 being interconnectedby the table 13% may slide forwardly or rearwardly on the rails 51.Extending outwardly from the forward edge of wall 121 adjacent its lowerend is a vertical lip 121a disposed below the lower edge of the rails.Fixed to wall 121 of each carriage and extending outwardly therefrom isa pin 135 disposed just above the upper edge of the rail 51.

A typewriter, or other instrument not shown, may be fixed or attached tothe top of the table 130 in any suitable manner. While this device isdescribed as a pull out support for a typewriter, it will be understoodthat any other article or oiiice machine may be attached to the table130 and this invention is not limited to typewriter supports.

It will now be understood that the springs 1% keep the rails 51 in theirrearwardly position at a level below the fixed bars 21. It will also beunderstood that the carriages and table may roll freely back and forthon the rails 51. Therefore, the table 130 may be pushed all the Fixed towall 121 and disposed be- 5 way back on the rails 51 so that thetypewriter or other article supported thereon will be wholly housedwithin the desk.

To release the locking levers 165 so as to permit the table 130 togetherwith the rails 51 to be swung frwardly and then upwardly about the bellcranks 26, 55 it is necessary to first pull the table 130 forwardly. Asthat is done the pins 135 will engage within the slots 107, as shown inFig. 6 of the drawing, to rotate the locking levers 105 in acounterclockwise direction against the tension of the springs 115. Whenthe carriage is pulled entirely forwardly the locking levers Hi willrotate about the pivot pins 102 to positions where the fingers 113contact the top edges of locking members 40. In such position the pins135 will be located adjacent the edges 45 of said members 40.

The front ends of the rails 51 are interconnected by a horizontaltransverse rod 51:: fixed thereto. Said rails are furthermoreinterconnected adjacent their rear ends by a horizontal transverse rod51.) fixed thereto. When the carriages and table have been pulledforward to their forwardmost position the front edges 121a of the sidewalls 121 of the carriages will contact the front cross bar 51a to stopfurther movement of the table or carriages in the forward direction, andto maintain the pins 135 substantially in contact with the edges ofmembers 46.

When the locking levers 135 have been rotated fully in counterclockwisedirections, they will be held in such positions because the openings 116which are normally located above the pivots 192 will have moved belowthe pivot pins li 5 so that the springs 115 will retain the lockinglevers in their releasing positions. When said locking levers have beenrotated by the carriages and released, further forward movement of thetable will cause the rails 51 to move forwardly therewith, and as soonas the pivot points 94 have moved forwardly of a line interconnectingthe axis 6 with the axis 80, the springs 109 will exert upward pull onthe rails to raise the rails 51, carriages 12th, and table 13% togetherwith the typewriter or other article thereon, and to cause a swinging ofthe bell cranks 26 and in a clockwise direction about the pivots 25 and64, bringing the parts to the position shown in Fig. 3. During suchmovement the brackets 88 will likewise swing in a clockwise direction toa position shown in Fig. 3, the hooks which pivot freely about thepivots 94 will be moved to the position shown in Fig. 3 and the springswill exert an upward pull through the hooks 95 on the brackets 83 toretain the table 131' in its raised position.

Releasable catch means is provided for retaining the table 139 in raisedposition. To this end there is fixed to the cross bar 18 as by screw 140a plate 141 provided with a forward and downwardly inclined lower flange149a. Said plate 141 is formed with a V shaped notch 142 at its lowerend, widening toward the bottom. Also fixed to the cross bar 18 is anangle member 144 having a top flange 1 1-5 contacting the top of thecross bar 18 and screwed thereto as by screws 146. Extending downwardlyfrom wall 145 is a well 147 contacting member 1 11 and extendingtherebelow. Member 147 is formed with a vertical slot 148 aligned withthe notch 142 but extending therebelow.

Fixed to the top of the table 130 is a bracket 150 having a horizontalwall 151 screwed to the top of the table. Extending upwardly from thehorizontal wall 151 is a vertical wall 152 formed with a horizontalopening 153. Extending from the opening 153 is a pivot pin 154. Pivotedto the pivot pin 15 i is a lever 155. The lever 155 has a hooked head orcatch 156 at its upper end. It is provided with a handle 157. On thepivot pin 15 i is a collar 160. On the collar 160 is a torsion spring161 having one arm engaging a lip 162 on the lever and another armcontacting the horizontal wall 151 of the bracket 159. Torsion spring161 tends 7 to rotate the lever 155 in a clockwise direction, looking atFig. 11.

The head 156 is so located that as the table 130 comes up said head 156will pass first through the notch 142 and then through the slot 148,engaging the lower edge of the slot, and holding the table 130 againstaccidentally being pushed down or vibrating or side swaying. The notch142 being wide at its lower end serves to guide the head 156 to the slot148.

\Vhen it is desired to lower the table 136 the lever handle 157 isdepressed against the torsion spring to release the head 156, and thenthe table may be pulled down to its lowermost position. As that is donethe table is pushed back so that the pins 135 will engage the lingers1113 ard rotate the locking cams 105 in clockwise directions to lockingposition. The table can be pushed all the way back so that it is whollyhoused within the desk.

It will be observed that the outwardly pressed portions 57 of the rearbell cranks 55 provide channels or spaces for the pins 135 to be movedrearwardly as the table and carriages are pushed back in their lowermostposition. Furthermore, as the table is swung forwardly and raised saidoutwardly offset portions 57 move through the outwardly offset portions77 of the links 76 and during the operation of the device said offsetportions '77 move through the spaces afforded by the offset portions 23aof the bars 21. Thus, sufiicient clearance is provided for operating thedevice.

it will be observed that when the carriages and table 130 are movedforwardly sufliciently to release the locking cams 105 a slight movementforwardly against the bar 51:: is sufiicicnt to bring the axis of thepivots 94 from the back side of a plane passing through the axes of bars64 and 80 to the front side of said plane, and such movement willimmediately bring the coil springs into play to pull upwardly and toraise the typewriter desk 130 easily, even with the weight of thetypewriter or other article thereon.

It will thus be seen that there is provided a device in which theseveral objects of this invention are achieved and which is well adaptedto meet the conditions of practical use.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiment above set forth,it is to be understood that all matter herein set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

Having thus described my invention I claim as new and desire to secureby Letters Patent:

1. A device of the character described comprising a pair of parallelhorizontally aligned fixed bars, front bell cranks pivoted to said barsand having downwardly and forwardly extending arms, and forwardly andupwardly extending arms, cam means at the lower ends of the downwardlyextending arms and having outwardly curved peripheral edges and inwardlycurved peripheral edges, rear bell cranks pivoted to said bars andhaving downwardly and forwardly inclined arms and forwardly and upwardlyinclined arms, rails interconnecting the lower ends of said downwardlyextending arms of said bell cranks, links interconnecting the forwardlyand upwardly extending arms of said bell cranks, locking levers pivotedto said rails and having outwardly curved edges conforming to theinwardly curved edges of said cam means, a supporting member mounted forsliding movement on said rails, and means on said supporting member torotate said locking members in opposite directions to bring theoutwardly curved edges of said locking levers into and out of engagementwith the inwardly curved edges of said cam means.

2. A device of the character described comprising a pair of parallelhorizontally aligned fixed bars, front and forwardly extending arms, andforwardly and up wardly extending arms, cam plates fixed to the lowerends of the downwardly extending arms and having outwardly curvedperipheral edges and inwardly curved peripheral edges, rear bell crankspivoted to said bars and having downwardly and forwardly inclined armsand forwardly and upwardly inclined arms, rails interconnecting thelower ends of said downwardly extending arms of said bell cranks, linksinterconnecting the forwardly and upwardly extending arms of said bellcranks, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, springmeans to rotate the locking lovers in one direction, a supporting membermounted for sliding movement on said rails, and means on said supportingmember to rotate said locking members in an opposite direction to bringthe outwardly curved edges of said locking levers beyond the inwardlycurved edges of said cam plates, a fixed cross bar, brackets fixed tosaid rear bell cranks, hooks pivoted to said brackets, and springsinterconnecting said hooks with said fixed cross bar.

3. in combination, a pair of fixed parallel bars, bell cranks pivoted tosaid bars, links interconnecting the arms of said bell cranks to formparallelograms to permit swinging of said bell cranks together, a pairof said links constituting rails, carriages mounted on rollers on saidrails, a table fixed to said carriages and interconnecting the same, apair of said bell cranks having cam plates formed with inwardly curvededges, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, saidlocking levers being formed with slots opening above the rails, and pinson said carriages adapted to engage within said slots for rotating saidlocking levers upon moving the table and carriages forwardly, for movingthe outwardly curved edges of the locking levers beyond the inwardlycurved edges of the cam plates.

4. In combination, a pair of fixed parallel bars, bell cranks pivoted tosaid bars, links interconnecting the arms of said bell cranks to formparallelograms to permit swinging of said bell cranks together, a pairof said links constituting rails, carriages mounted on rollers on saidrails, 21 table fixed to said carriages and interconnecting the same, apair of said bell cranks having cam plates formed with inwardly curvededges, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, saidlocking levers being formed with slots opening above the rails, and pinson said carriages adapted to engage within said slots for rotating saidlocking levers upon moving the table and carriages forwardly, for movingthe outwardly curved edges of the locking levers beyond the inwardlycurved edges of the cam plates, said cam plates having outwardly curvedpart circular edges adapted to be engaged by said pins on said carriagesas said rails are swung about said bell cranks from a lower to an upperposition.

5. In combination, a pair of fixed parallel bars, bell cranks pivoted tosaid bars, links interconnecting the arms of said bell cranks to formparallelograms to permit swinging of said bell cranks together, a pairof said links constituting rails, carriages mounted on rollers on saidrails, a table fixed to said carriages and interconnecting the same, apair of said bell cranks having cam plates formed with inwardly curvededges, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, saidlocking levers being formed with slots opening above the rails, and pinson said carriages adapted to engage within said slots for rotating saidlocking levers upon moving the table and carriages forwardly, for movingthe outwardly curved edges of the locking bell cranks pivoted to saidbars and having downwardly 7-3 levers beyond the inwardly curved edgesof the cam plates, means on said locking levers to limit rotating of thelocking levers relative to said cam plates, and toggle spring means toaid in rotating said locking levers in one direction or another.

6. In combination, a pair of fixed parallel bars, bell cranks pivoted tosaid bars, links interconnecting the arms of said bell cranks to formparallelograms to permit swinging of said bell cranks together, a pairof said links constituting rails, carriages mounted on rollers on saidrails, a table fixed to said carriages and interconnecting the same, apair of said bell cranks having earn plates formed with inwardly curvededges, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, saidlocking levers being formed with slots opening above the rails, and pinson said carriages adapted to engage within said slots for rotating saidlocking levers upon moving the table and carriages forwardly, for movingthe outwardly curved edges of the locking levers beyond the inwardlycurved edges of the cam plates, and toggle spring means to lower therails at the end of the downward movement of said rails and to raisesaid rails when said carriages are moved forwardly to release thelocking levers.

7. In combination, a pair of fixed parallel bars, bell cranks pivoted tosaid bars, links interconnecting the arms of said bell cranks to formparallelograms to permit swinging of said bell cranks together, a pairof said links constituting rails, carriages mounted on rollers on saidrails, a table fixed to said carriages and interconnecting the same, apair of said bell cranks having cam plates formed with inwardly curvededges, locking levers pivoted to said rails and having outwardly curvededges conforming to the inwardly curved edges of said cam plates, saidlocking levers being formed with slots operiing above the rails, andpins on said carriages adapted to engage within said slots for rotatingsaid locking levers upon moving the table and carriages forwardly, formoving the outwardly curved edges of the locking levers beyond theinwardly curved edges of the cam plates, toggle spring means to lowerthe rails at the end of the downward movement of said rails and to raisesaid rails when said carriages are moved forwardly to release thelocking levers, and means on the carriages to engage the rails to pushthe rails forwardly upon moving the carriages fr wardly to change thetoggle spring action from pulling the rails down to an upward pulloperation of said toggle springs.

8. A device of the character described comprising a frame, front linkspivoted to said frame and having dOW"- wardly extending arms, cam meansfixed to the lower ends of the downwardly extending arms and havinginwardly curved peripheral edges, rear links pivoted to said frame andhaving downwardly inclined arms, rails interconnecting the lower ends ofsaid downwardly extending arms f said links, locking levers pivoted tosaid rails and having outwardly curved edges conforming to the inwardlycurved edges of said cam means, a supporting member mounted for slidingmovement on said rails, and means on said supporting member to rotatesaid locking mer bers in opposite directions to bring the outwardlycurved edges of said locking levers into and out of engagement with theinwardly curved edges of said cam means.

9. A device of the character described, comprising a member, a pair ofbell cranks pivoted to said member at spaced points, each bell crankhaving a first and a second arm, link means to interconnect the firstarms of said bell cranks, table support means mounted on said linkmeans, link means to interconnect the second arms of said bell cranks,one of said bell cranks having a curved edge, a pivoted locking elementhaving a curved edge complementary to the curved surface of said bellcrank, the center of curvature of said edges being coincident with thepivotal axis of said locking element, and means to rotate said lockingelement to engage or disengage said curved edges thereby to lock orunlock said bell cranks against rotary movement.

10. In combination a rail member, a carriage slidable on the rail memberand movable from a rear position to a front position, a supportingmember associated with the carriage and movable with the carriage fromsaid rear position to said front position, means to elevate thesupporting member from a lower front position to an elevated frontposition, means to lock the supporting member against being elevatedfrom its lower position as it is moved from the rear position toward thelower front position, and means to release said locking means as thesupporting member reaches its lower front position, said locking meanscomprising a pivoted elevating member which is part of the elevatingmeans and being formed with a curved edge, and a pivoted locking memberhaving a complementary curved edge adapted to engage the curved edge onthe pivoted elevating member when the supporting member is in its lowerposition rearwardly of the front position thereof to lock saidsupporting member against being elevated until said carriage reaches itsfront position, and means to rotate said locking member to disengage thecurved edge thereof from the curved edge of the pivoted elevating memberwhen the carriage reaches its front position to permit the supportingmemher to be elevated by said elevating means when said supportingmember reaches its lower front position.

11, In combination, a rail member, a carriage member slidable thereon,from a front position to a rear position, a support movable with thecarriage from front to rear, means to elevate said support from a lowerto an elevated position when said carriage is in its front position,said elevating means comprising a pivoted elevating link having alocking portion, a locking element pivoted to one of said members, andhaving a locking portion adapted to engage the locking portion of thepivoted link to prevent elevating of said support in a first angularposition of said locking element, and to disengage from said lockingportion of said link in a second angular position of said lockingelement, and means on the other of said members to positively engage androtate said locking element from the first angular position thereof tothe second angular position thereof, and to positively hold said lockingelement in said second angular position when said carriage reaches itsfront position, to release said pivoted lever and permit elevation ofthe support by said elevating means, and to positively engage and rotatesaid locking element in an opposite direction from its second positionto its first position when said carriage is moved rearwardly from itsfront position to lock said lever and prevent elevation of said supportas soon as said carriage moves rearwarclly away from its front position.

References Cited in the file of this patent UNITED STATES PATENTS1,178,220 Dietz Apr. 4, 1916 1,415,909 Vaaler May 16, 1922 1,904,217 FoxApr. 18, 1933 2,402,412 Koch June 18, 1946 2,524,386 Johnston Oct. 3,1950 FOREIGN PATENTS 579,591 Germany June 15, 1933

